This research proposal seeks to delineate the pathophysiologic mechanisms involved in the hypoglycemia frequently seen in small for gestational age (SGA) newborns. It seeks to do this by a prospective study during the first six hours following birth of the metabolic sequence involved in the adaptation to extrauterine fasting. Particular emphasis will be placed on capacity for gluconeogenesis, availability of substrate for gluconeogenesis, availability of alternate fuels and hormonal milieu. These studies will compare the patterns observed in SGA infants who maintain normoglycemia, SGA infants who become hypoglycemic, premature infants who are appropriate for gestational age (AGA) who maintain normoglycemia, AGA prematures who develop hypoglycemia, and full term normoglycemia AGA newborns. BIBLIOGRAPHIC REFERENCES: Baker, L., Minuchin, S., Milman, L., Liebman, R. and Todd, T.: Psychosomatic Aspects of Juvenile Diabetes Melitus: A Progress Report. In: Modern Problems in Pediatrics, Vol. 12. Karger, Basel, 1975. Moshang, T., Jr., Parks, J.S., Baker, L., Vaidya, V., Utiger, R., Bongiovanni, A., and Snyder, P.S.: Low Levels of Triiodothyroxine in Patients with Anorexia Nervosa. J. Clin. Endo. and Metab., 40-468, 1975.